Computer memory is a technology consisting of semiconductor devices arranged to retain digital data. It is a fundamental component of computers. Resistive random access memory (RRAM) and magnetic random access memory (MRAM) are two types of memory garnering attention.
In RRAM, the basic idea is that a resistance of a dielectric can be changed to store different states depending on the voltage applied to it. To form an array, a number of memory elements can be arranged in a configuration where parallel bitlines are crossed by perpendicular wordlines with the variable resistance dielectric placed between wordline and bitline at every cross-point. This configuration is called a cross-point cell. Unfortunately, since this architecture can lead to a large “sneak” parasitic current flowing through non selected memory cells via neighboring cells, the cross-point array has a very slow read access. An access element can be added to improve the situation, but conventional access elements consume significant area on the chip. The present disclosure relates to vertical bipolar junction transistors (BJTs) that can be used as access elements to reduce the area of individual memory cells, thereby increasing the density of the memory array.